使用这样的sql语句查询对主键排序特别慢，这是为什么呢，有什么解决办法吗
select * from alarm_log order by ts desc limit 0,10;
貢獻者指南
技術棧
csql
領域
databaseperformance
議題類型
performance
難度面向新貢獻者的預計實作難度，1 表示很小改動，5 表示專家級工作。
3
預計時間有經驗貢獻者完成調查、實作、測試並準備 pull request 的粗略時間範圍。
1-3 hours
活動狀態議題目前的可參與程度：新鮮、活躍、陳舊、阻塞或等待維護者輸入。
fresh
清晰度議題是否清楚說明預期改動、驗收標準和下一步。
needs investigation
前置要求
Basic understanding of TDengineSQL query optimization concepts
新手友善度1-100 的估計分數，表示該議題對首次貢獻者的友善程度。
20
研究方向
The issue lacks schema details (e.g., number of columns, data volume), query execution plan, and whether the super table's primary key is properly indexed. First, check if the user has provided a reproducible test case in the comments. Look at the query execution path in TSDB: examine the order by implementation in the source code (likely in `tsdb/` directory). Verify if the query uses the primary key index or performs a full scan. Search for similar reported issues in the repository. If possible, replicate the slow query with a simple schema and measure performance with and without order by. Provide guidance on using EXPLAIN to get query plan.
